vacuum advance with a dellorto
 

well im installing a dellorto 48 on the DD today. i have a concern, the vacuum advance. i know its debatable if you need it or not. i know the advantages are better gas milage and maybe a little performance, but arent *needed*. i have the same setup on my SP 13b in my project car without the advance hooked up. id like to run it on my DD though. one question, when drilling the hole for the tap, would it be better in a primary or secondary port? i also plan on playing with the timing a little today for the first time. maybe be figure out a good setting for a little more go, and then use stock for better ecomony. any input is appreciated. thanks.

I recommend keeping vac advance. Your car will run like shiz without. And as far as performance goes, your not going to notice anything significant. So just time it to the recommended timing.

but where does the advance need to be hooked up, primary or secondary?

I wouldn't worry about vacuum advance.

Intetresting how there are two opinions on the subject. :)

well, since i cant decide where to put it, i wont be running it. doesnt matter now. due to crappy OMP lines i have to wait till i can get replacements before i can run the car.

just premix till you get your lines fixed not that big of a deal^^^

^^ thought about that as well, probably what ill do since i have a whole case of indemitsu premix:) well time to get back to work.

Actually, neither. The vacuum advance needs to hooked to a venturi vacuum, that only draws vacuum when the throttle is opened. Not manifold vacuum.
Venturi vacuum is found above the throttle plates. As the flow increases thru the venturis, due to the throttle plates opening, the advance will start to get it's vacuum, and thereby advance the timing as the engines load increases.

I have my 45DCOE on a 12A SP with the vacum advance disconnected. Plugged the vacum and advance the ignition timming by about 5degrees.....

It's been working great....

You all are crazy. Your crippling your cars performance(slightly) and economy, simply because you are to scared to hook a vac line up

Give the man a cigar!!! Manifold vacuum drops when the throttle plates open. Ever watch a vacuum gauge on a running engine?

A nice cuban does sound good....:icon_tup:

I knew I was leaving out part of the statement I was trying to make....:wallbash:

i have some omp lines if you want, free +shipping

With good reason. If not done correctly, you can seriously damage your engine. As my dumb ass proved. It isn't worth it if you are'nt 100% positive on the proper way to run it.

where would you sudjest the nipple be places on a set up like this then? you dont have very many options.

im going to try a permanent replacement with some stuff for lawn mowers and hopefully itll work. if not, ill definately take that offer. thanks

The nipple needs to be on the carb. Unfortunately, some sidedraft carbs do not have this made into them, as they are originally designed for racing, and most racers are more interested in where the total advance falls at XXXXRPM, and don't need the extra help down low in the RPM range.
Look your carb over, and see if there is an existing vacuum port on the throttle plate, or near it. Once (or if) you find one, check to see if it pulls vacuum at idle. A venturi vacuum port will pull little to no vacuum at idle, but once you start to open the throttle, it will start to pull more vacuum. If you find a port that matches this behaviour, thats the one for the advance. Just use a "T" to hook up both pods.

^^ill check tomorrow, but im 99% sure one doesnt exist on the carb. the only nipples already available is the one on the manifold for the brake booster, the OMP nipples, and one in the filter plate(probably use for PCV connection.

Do you have the original RB instructions for your Dell? I'm pretty sure it instructs to leave the vacuum ports disconnected. And, I don't think you're supposed to cap them, rather leave them open to the air. I can't remember the rationale, but I recall that capping them could lead to undesirable or erratic timing for some reason. You might want to do a search on this issue. Personally, I left mine disconnected and uncapped and never had any problems with it.

I just remembered this. I have seen a couple sidedrafts carbs that had a threaded hole with a plug in them. This *may* be for the vac. advance, if so desired.
Check the OMP nipples, if they act in the correct manner, you could use one of those, and make new nipples in the intake for the OMP hoses, or just go to premixing.

The vacuum pots are left uncapped so the advance can work. Capping them off will prevent the normal internal advance.

On the Mikunis for the 12As, there's a nipple in each barrel. On the SE carbs, those nipples are plugged. I would need to look at mine to see if they are before or after the butterflys. I think they are after

i know the RB instructions say to not hook up the advance, but id like to try running it if its not too much trouble. i think its help out economicly.



slacking:D i was wondering how long itd take you to show up;) so what advice do you have for me? ill check my carb today and see what i can find.

heres what i found. i dont know what these are for. maybe theyll work?

the way the holes are one hole is after the butterfly when the throttle is closed and as the throttle progresses to open more holes are behind the butterfly.

i looked in my "how to build and power tune weber and dellorto" book and it says that screw is for a progression hole. when i looked to see what its for it says, "the cover was put there in the first place to allow for the progression holes to be drilled but it also doubles as a removeable plug for cleaning purposes.."

That screw-in brass nipple,in the 3rd pic, is that just above the throttle plates?

the holes are as i described above. they are right on the line of the butterfly, right below the bottom of the choke.

Ah, on the other end. It was so close up, I couldn't tell if that was throttle plate, or choke. Had it been throttle plates, it woulda been perfect.......
It may be too high to pull a proper venturi vacuum. I'm guessing the other nipple in that pic is the OMP port, and has a matching one on the other barrel. Also looks too far away from the throttle plates to pull a proper venturi vacuum.